Later today, Firefox will undergo its biggest developmental upheaval ever. Mozilla-central, the source of nightly builds, will be renumbered to version 5 -- and at long last, after years of wallowing around version 1, Mozilla's rendering and layout engine, Gecko, will also have its version number updated to match Firefox.

In other news, if you want to take a sneak peek at the new 'channel changing' technology that will be introduced in upcoming Firefox builds, head to about:config and create a new string called app.update.desiredChannel -- the value doesn't matter. Then open Help > About Firefox and you'll be able to switch channel, but it doesn't do anything just yet (image after the break). Here's hoping that Firefox channel switching is smoother than Chrome.